In the development of heating equipment, including combustion furnaces, particularly for use in heating enclosed spaces, there has been a continuing need to provide a heater which is compact, economical to manufacture and energy efficient. Conventional combustion furnace type heaters, for example, include separate heat exchanger and blower or fan housing structures which are disposed within a generally rectangular box-like cabinet having an air inlet opening for so-called return air and an air outlet opening for so-called supply air. However, the requirements mentioned above with respect to overall physical size of the heater or furnace, the cost of manufacture and energy efficiency continue to be motivating factors for further developments and it is to these ends that the present invention has been developed.